function [gtc_img, gtc_param] = gtc2geotiff(gtc_path, dem_par_path, varargin)
    [gtc_img, gtc_param] = gamma.readDem(gtc_path, dem_par_path);
    gtc_refer = gamma.demParam2refer(gtc_param);
    gtc_img = sqrt(gtc_img);
    if nargin == 3
        geotiffwrite(varargin{1}, gtc_img, gtc_refer);
    end
end
